Volume 11 Issue 1

An enzymatic mild acidic hydrolysis was used to separate and purify residual lignin from alkaline peroxide mechanical pulp (APMP). Using the optimum conditions for the laccase treatment (pH 4.5, temperature 50 °C, lignin consistency of 1%, a reaction time of 60 min, and a laccase dosage of 8 μ/g), oven-dried lignin was treated with laccase and in a laccase mediator system (LMS) to explore the mechanism for laccase and the LMS modification of APMP. The changes of functional groups in lignin were analyzed using nuclear magnetic resonance (31P-NMR and 13C-NMR). The molecular weight distributions of the lignin samples were confirmed by gel permeation chromatography (GPC). The 31P-NMR and 13C-NMR spectra revealed that the lignin structure changed significantly with the laccase and the LMS treatments. Meanwhile, GPC demonstrated that laccase without a mediator could lead to the polymerization of lignin, while the LMS could degrade the lignin. Hence, it was concluded that laccase is an attractive enzyme for lignin modification.

To modify the acoustic properties of dawn redwood (Metasequoia glyptostroboides Hu et Cheng), thermal, ultrasonic, and combined thermal-ultrasound treatments were employed in this work. The changes in the logarithmic decrement (δ), specific Young’s modulus (E’/ρ), and extractives content were examined. The results showed that thermal and ultrasonic treatments were both essential for a decrease in the logarithmic decrement (δ) and an increase in the specific Young’s modulus (E’/ρ) of dawn redwood (Metasequoia glyptostroboides Hu et Cheng). A superposition effect on decreasing of the logarithmic decrement (δ) was discovered after thermal-ultrasound combined treatment. The amounts of extractives, extracted by 95 °C distilled water, 1% NaOH solution, and benzene-ethanol solution, decreased after thermal and ultrasonic treatments. Moreover, there was a linear correlation between logarithmic decrement (δ) and extractives, in which extractives from 1% NaOH solution and 95 °C distilled water had a significant effect. Finally, dawn redwood samples treated with ultrasonic power at 340 W for 9 min at a thermal temperature of 200 °C were chosen as the optimal method in this research.

A biomass gasification model was developed using Aspen Plus based on the Gibbs free energy minimization method. This model aims to predict and analyze the biomass gasification process using the blocks of the RGibbs reactor and the RYield reactor. The model was modified by the incomplete equilibrium of the RGibbs reactor to match the real processes that take place in a rice husk gasifier. The model was verified and validated, and the effects of gasification temperature, gasification pressure, and equivalence ratio (ER) on the gas component composition, gas yield, and gasification efficiency were studied on the basis of the Aspen Plus simulation. An increasing gasification temperature was shown to be conducive to the concentrations of H2 and CO, and gas yield and gasification efficiency reached peaks of 2.09 m3/kg and 83.56%, respectively, at 700 °C. Pressurized conditions were conducive to the formation of CH4 and rapidly increased the calorific value of syngas as the gasification pressure increased from 0.1 to 5 MPa. In addition, the optimal ER for gasification is approximately 0.3, when the concentrations of H2 and CO and the gasification efficiency reach peaks of 23.65%, 24.93% and 85.92%, respectively.

The enzyme involved in hexenuronic acid (HexA) removal from kraft pulp was identified in Paenibacillus sp. strain 07. Extracellular and intracellular enzymes of Paenibacillus sp. were assessed for their hexenuronosyl-xylotriose (∆X3) degradation activity. First, ∆X3 was obtained from hardwood kraft pulp by enzymatic hydrolysis using three commercial enzymes. Crude extracellular and intracellular enzyme fractions were obtained from Paenibacillus cultures cultivated in 0.5% (w/v) birch wood xylan as the sole carbon source. The ∆X3-degrading activities of the enzyme fractions were measured by hydrolysis assays in sodium acetate buffer containing ∆X3 substrate (pH 6) at 50 °C. The reaction products were analyzed by high-performance anion-exchange chromatography with pulsed amperometric detection. The enzyme fractions displayed different chromatogram patterns. After treatment with the intracellular enzyme fraction, the chromatograms displayed xylose and hexenuronosyl xylobiose (∆X2) peaks. The chromatogram patterns of the extracellular fraction assays indicated xylose, xylotriose, and ∆X2 production. Thus, the intracellular enzymes of Paenibacillus can hydrolyze the xylosidic linkages at the reducing ends of ∆X3, whereas a specific extracellular enzyme can hydrolyze HexA. This enzyme is potentially applicable to HexA removal during bio-bleaching.

This study investigated the degradation and enzymatic saccharification of cornstalk by white-rot and brown rot fungi. The fungal strains Trametes pubescens Cui 7571, Trametes velutina Dai 10149, and Antrodia wangii Cui 7568 were analyzed in solid-state fermentation cultures. Various extracellular enzyme activities were assessed to determine biochemical changes during the degradation process. Fourier-transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) analysis were used to determine the structural changes. A correlation analysis between the chemical composition of cornstalk, extracellular enzyme activities, and structural changes indicated that T. pubescens Cui 7571 broke down lignin efficiently and subsequently degraded cellulose, and hemicellulose digestion was not affected by the lignin barrier. Enzymatic hydrolysis demonstrated that the T. pubescens Cui 7571-pretreated samples increased cellulose and hemicellulose conversion in cornstalk. Overall, T. pubescens Cui 7571 displayed excellent performance as a biological pretreatment agent, and lignin played a significant role in the enzymatic saccharification of cornstalk.

This work investigated the efficiency of a tetraacetylethylenediamine/ hydrogen peroxide/triethanolamine (TAED/H2O2/TEA) system for low-temperature bleaching of cotton fabric, with and without ultrasonic assistance. The low-temperature bleaching results were compared to those obtained from a conventional H2O2 bleaching system. The application of TAED/H2O2/TEA without ultrasonic assistance to grey cotton fabric with a whiteness index (WI) of 28 and tenacity of 40 CN/Tex resulted in full bleaching of the cotton fabric at 70 °C within 60 min. This low-temperature bleaching system produced a bleached cotton fabric with a WI of 69 and tenacity of 38 CN/Tex, while the conventional H2O2 bleaching system gave a bleached cotton fabric WI of 73 and tenacity of 32 CN/Tex. The application of ultrasound to a low-temperature bleaching system showed a reduction in the duration required for full bleaching to 30 min rather than 60 min and gave bleached fabrics of the same physiochemical properties.

A simple, environmentally friendly, and efficient synthesis method for cellulose/silver (Ag) nanocomposites was developed by microwave heating an alkaline aqueous solution of cellulose fiber and silver nitrate (AgNO3), which resulted in good utilization of silver ions and a product with high silver content. The effect of the alkaline compounds and reducing agents on the silver content and utilization rate of silver ions was investigated using atom absorption spectroscopy (AAS). The morphology, size, thermal stability, and surface components of cellulose/Ag nanocomposites were investigated using scanning electron microscopy (SEM), thermogravimetric analysis (TG), differential scanning calorimetry (DSC), and Raman spectroscopy. The alkaline compound and reducing agent influenced the size and shape of the silver nanoparticles. Reduced silver ions had the greatest influence on the surface components of cellulose; however, nano-silver particles exhibited no obvious influence on cellulose’s thermal stability. Furthermore, cellulose/Ag nanocomposites exhibited excellent antibacterial activity against Escherichia coli and Staphylococcus aureus.

Arbutus andrachne and Platanus orientalis grow naturally in Turkey. They do not occur in stands but can be seen as solitary trees. A. andrachne is seen in coastal parts of Anatolia, whereas P. orientalis can be found from west to the east of Turkey, mostly in river banks. Lipophilic extractives, hydrophilic extractives, and suberin monomers from Arbutus andrachne and Platanus orientalis bark was analyzed by chromatography. The total amount of lipophilic extractives was higher in P. orientalis (8.55 mg/g). However, the total amount of hydrophilic extractives had a bigger proportion, 100.86 mg/g, in A. andrachne bark. Dioic and hydroxy acids were the dominant group in the suberin monomers of both species of bark. Acid 1,18-dioic-18:0 and acid 18-hydroxy-18:1 were determined as the main compounds of suberin monomers in both samples. In addition, total amount of suberin monomers was determined to be 11.36 mg/g in A. andrachne and 15.95 mg/g in P. orientalis bark.

Epoxidized (EHO) and acrylated (AEHO) bio-resins from hemp oil were synthesized, and their interpenetrating networks (IPNs) were investigated in reinforced bio-composites with natural jute fibres and glass fibres. The mechanical properties (tensile, flexural, Charpy impact, and inter-laminar shear) and viscoelastic properties (glass transition temperature, storage modulus, and crosslink density) of the bio-resins and their hybrid IPNs EHO/AEHO system were investigated as a function of the level of bio-resin hybridization. The hybrid bio-resins exhibited interpenetrating network (IPN) behaviour. Composites prepared with the synthetic vinyl ester (VE) and epoxy resins showed superior mechanical and viscoelastic properties compared with their bio-resins and IPNs-based counterparts. With glass fibre (GF) reinforcement, increases in the EHO content of the IPNs resulted in increased stiffness of the composites, while the strength, inter-laminar shear strength (ILSS), and impact resistance decreased. However, in the jute fibre reinforced bio-composites, increases in AEHO content generated increased tensile modulus, ILSS, and mechanical strength of the bio-materials. Crosslink density and glass transition temperature (Tg) were also higher for the synthetic resins than for the bio-resins. Increased AEHO content of the IPNs resulted in improved viscoelastic properties.

Cymbopogon citratus orlemon grass, is a potential renewable herbaceous biomass alternative. Lemon grass contains silica, which is available for extraction as a filler for various applications. Lemon grassash is produced at calcination temperatures of 0, 400, 525, 600, and 700 ˚C. The silica content of the lemon grass ash was characterized by X-ray fluorescence (XRF), X-ray powder diffraction (XRD), scanning electron microcopy (SEM), and Fourier transform infrared (FTIR) analysis. The shape and texture of the lemon grass ash were studied by SEM. The highest silica content recorded was 24.00% for lemon grass calcined at 400 °C. The porosity of the lemon grass ash increased as the calcination temperature increased from 0 °C to 700 °C. XRD analysis showed that the crystallinity of silica in the lemon grass ash increased with increasing calcination temperature. FTIR analysis confirmed the presence of organic structure in lemon grass without calcination and the inorganic structure of siloxane and silanol bonds present in lemon grass calcined at different temperatures.